Commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (now U.S. Pat. No. 4,576,211, issued Dec. 19, 1995), and its counterpart commonly-owned copending "divisional" U.S. patent applications Ser. Nos. 08/457,479 filed Jun. 1, 1995 (U.S. Pat. No. 6,049,976) and Ser. No. 08/570,230 filed Dec. 11, 1995 (U.S. Pat. No. 5,852,871), all by KHANDROS, disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire "stem" or "skeleton") to a terminal on an electronic component, coating the flexible core element and adjacent surface of the terminal with a "shell" of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.
Commonly-owned, copending U.S. patent application Ser. No. 08/340,144 filed Nov. 15, 1994, U.S. Pat. No. 5,917,707 and its corresponding PCT patent application No. PCT/US94/13373 filed Nov. 16, 1994 (WO95/14314, published May 26, 1995), both by KHANDROS and MATHIEU, disclose a number of applications for the aforementioned spring contact element, and also discloses techniques for fabricating contact pads at the ends of the spring contact elements. For example, in FIG. 14 thereof, a plurality of negative projections or holes, which may be in the form of inverted pyramids ending in apexes, are formed in the surface of a sacrificial layer (substrate). These holes are then filled with a contact structure comprising layers of material such as gold or rhodium and nickel. A flexible elongate element is mounted to the resulting contact structure and can be overcoated in the manner described hereinabove. In a final step, the sacrificial substrate is removed. The resulting spring contact has a contact pad having controlled geometry (e.g., sharp points) at its free end.
Commonly-owned, copending U.S. patent application Ser. No. 08/452,255 filed May 26, 1995 pending and its corresponding PCT patent application No. PCT/US95/14909 filed Nov. 13, 1995 (WO96/17278, published Jun. 6, 1996), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose additional techniques and metallurgies for fabricating contact tip structures on sacrificial substrates, as well as techniques for transferring a plurality of spring contact elements mounted thereto, en masse, to terminals of an electronic component (see, e.g., FIGS. 11A-11F and 12A-12C therein).
Commonly-owned, copending U.S. Provisional Patent Application No. 60/005,189 filed May 17, 1996 and its corresponding PCT patent application No. PCT/US96/08107 filed May 24, 1996 (WO096/37332, published Nov. 28, 1996), both by ELDRIDGE, KHANDROS, and MATHIEU, discloses techniques whereby a plurality of contact tip structures (see, e.g, #620 in FIG. 6B therein) are joined to a corresponding plurality of elongate contact elements (see, e.g., #632 of FIG. 6D therein) which are already mounted to an electronic component (#630). This patent application also discloses, for example in FIGS. 7A-7E therein, techniques for fabricating "elongate" contact tip structures in the form of cantilevers. The cantilever tip structures can be tapered, between one end thereof and an opposite end thereof. The cantilever tip structures of this patent application are suitable for mounting to already-existing (i.e., previously fabricated) raised interconnection elements (see, e.g., #730 in FIG. 7F) extending (e.g., free-standing) from corresponding terminals of an electronic component (see. e.g., #734 in FIG. 7F).
Commonly-owned, copending U.S. Provisional Patent Application No. 60/024,555 filed Aug. 26, 1996, by ELDRIDGE, KHANDROS and MATHIEU, discloses, for example at FIGS. 2A-2C thereof, a technique whereby a plurality of elongate tip structures having different lengths than one another can be arranged so that their outer ends are disposed at a greater pitch than their inner ends. Their inner, "contact" ends may be collinear with one another, for effecting connections to electronic components having terminals disposed along a line, such as a centerline of the component.
The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term "fine-pitch" refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 .mu.m. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.